Gas blast circuit breaker having both bulged-out portion in hollow insulator and gas flow guide tube adjacent switching members



Aug. 6, 1968 H. SCHUBERT ETAL 3,396,253 GAS BLAST CIRCUIT BREAKER HAVING BOTH BULGED-OUT PORTION IN HOLLOW INSULATOR AND GAS FLOW GUIDE TUBE ADJACENT SWITCHING MEMBERS Filed July 16, 1965 INVENTORS Hel mut h Sch ubert Janis vitins ATTORNEY S United States Patent 3,396,253 GAS BLAST CIRCUIT BREAKER HAVING BOTH BULGED-OUT PORTION IN HOLLOW INSULA- TOR AND GAS FLOW GUIDE TUBE ADJACENT SWITCHING MEMBERS Helmuth Schubert and Janis Vitins, Wettingen, Switzerland, assignors to Aktiengesellschaft Brown, Boveri & Cie, Baden, Switzerland, a joint stock company Filed July 16, 1965, Ser. No. 472,423 Claims priority, application Switzerland, July 24, 1964, 9,703/ 64 5 Claims. (Cl. 200-148) ABSTRACT OF THE DISCLOSURE An electrical circuit breaker of the gas blast type in cludes a pair of coaxially arranged switching members that separate within a bulged out portion of a hollow insulator which serves as a quenching chamber. In order to maintain an essentially laminar flow of pressurized gas to the point at which the switching members separate, a gas supply tube concentrically surrounds one of the switching members which is stationary in radially spaced relation to establish an annular gas flow passageway and the discharge end of this gas supply tube terminates adjacent the end of the stationary switching member so as to deliver the gas to the switching point.

The present invention relates to an air blast circuit breaker with at least one switching point located within a hollow insulator, and which comprises a stationary switching member arranged concentrically to the hollow insulator and a movable, nozzle-shaped switching member, having on its contact side an umbrella or dish-shaped expanded portion, wherein an annular channel between the hollow insulator and the stationary switching member serves as air blast supply line to the switching point during the switching off operation and wherein the hollow insulator is expanded within the zone of the switching point.

With air blast circuit breakers it is already known to arrange the switching point within a hollow insulator forming the switching chamber, into which the quenching medium flows from one side 'to effect the switching off. Advantageously, the inner wall of the hollow insulator is here cylindrical in order to produce favorable i.e. essentially laminar flow conditions which essentially eliminates turbulence. On the other hand, it is also desirable to arrange the inner diameter of the chamber insulator within the zone of the switching point so large that it offers willcient place for the nozzle dish of the one switching member, which assists in guiding of the medium, whilst the dish simultaneously prevents substantially the forming of deposits on the inner surface of the hollow insulator. For this reason, quenching chamber insulators have already been constructed with an expanded inner diameter at the desired point, but without designing the insulator with a large diameter over its entire length. By this means, the end fittings of the insulator, such as flanges and the like, could be kept small, which is also desirable from the viewpoint of the internal stresses affecting the joints. However, both these postulates, namely, favorable flow conditions for the supply 'of the medium and a large inner diameter at the switching point, cannot be met easily at the same time so that hitherto an unsatisfactory compromise had to be accepted.

The invention has therefore thet object of providing a simple solution of this problem, thereby avoiding the drawbacks encountered in the known constructions. According to the invention, this object is realized in that 3,396,253 Patented Aug. 6, 1968 'ice there is provided a gas tube protruding into the expanded portion of the hollow insulator, surrounding the stationary member concentrically and extending to near the contact end of the movable switching member. In this way, the switching performance of air blast circuit breakers, equipped with this device, can be substantially improved, especially under difficult working conditions, such as are present, for example, with phase opposition or remote short circuits.

The invention will be further described, by way of example, with reference to the accompanying drawing, showing an embodiment of the invention in central longitudinal section.

A tubular hollow insulator 1, the center portion of which is expanded or bulged, contains a stationary, nozzleshaped switching member 2 and a movable switching member 3, having on its contact side an umbrella-shaped expanded part 3a. The switching member 2 is concentrically surrounded by a cylindrical gas supply tube 4 which projects into the bulging portion of the hollow insulator 1 and extends to near the upper contact end of the switching member 2. This gas supply tube 4 may be made of metal and is firmly mounted in the lower cylindrical part of the hollow insulator 1. If this is desirable from the point of view of the internal electric strength of the switching chamber, the gas supply tube 4 may also be made of insulating material. The gas supply tube 4 may also be equipped with radial bores 4a, whereby the possibility of deposits, such as of metal vapor, is avoided in the space between the gas supply tube 4 and the hollow insulator 1. Finally, the annular channel 5 serving for supplying the quenching medium, may contain a conical equalizing grating 6, made of perforated sheet metal and serving for the equalizing of the flow of pressurized gas, as known in the art. Preferably, this grating 6 extends to near the switching point whereby its efiiciency is substantially increased.

The operation of the arrangement is as follows: For the breaking, pressurized gas is supplied through the annular channel 5. As is evident from the drawing, since the gas supply tube 4 is cylindrical, i.e. it has a uniform diameter and is concentric with the tubular switching member 2 which is also cylindrical, the gas flow through the annular channel 5 to the point at which the switching members separate will be esssentially laminar, i.e. without turbulence notwithstanding the fact that the interior of the hollow insulator insulator 1 is bulged out in the vicinity of such point. As indicated by the arrows, the pressurized gas flows through the equalizing grating 6 and enters between the opening switching members 2 and 3, Where it is deflected by the umbrella-shaped wider portion 3a and escapes through the interior of the switching members. The movable switching member 3a is thereby moved longitudinally of itself into the switched off position as depicted in the drawing. To this end, it is equipped with an actuating piston, such as known in the art, and not shown in detail. The arc forming between the separating members 2 and 3 is blown, as known per se, in opposite directions into the interior of the switching members and is quenched. A small portion of the pressurized gas passes through the radial bores 4a in the gas supply tube 4 and removes any possible metal vapor deposits from the space between the parts 1 and 4. In the selected embodiment shown the switchgear members 2 and 3 open only for a short duration during the switching off, and these cooperate, as known in the art, with a serially connected electric voltage isolating switching device. The power switching members 2 and 3 re-close again after a short period, for example, under the action of a closing spring, not shown in detail, when the supply of pressurized gas is discontinued and the voltage isolating switch has taken over the insulation of the disconnected switch.

The invention is not limited to the embodiment herein described. Thus, for example, the fixed switching member 2 may be a solid switching pin, in which event the pressurized gas discharges solely through the interior of the hollow switching member 3.

We claim:

1. In an electrical circuit breaker of the gas blast type, the combination comprising a generally cylindrical hollow insulator, a pair of switching members arranged coaxially within said hollow insulator and spaced from the inner wall thereof, one of said switching members being hollow and including an umbrella shaped nozzled end adapted to be moved longitudinally of itself into and out of engagement with the confronting end of the other and stationary cylindrical switching member at a bulged-out part of the interior of said hollow insulator, and a cylindrical pressurized gas supply tube located within said hollow insulator and which concentrically surrounds said stationary switching member in radially spaced relation to establish an annular gas flow passageway therebetween, the end of 20 5 5 said gas supply tube terminating adjacent that end of said stationary switching member which engages the nozzled end of said movable switching member and serving to deliver the pressurized gas to the switching point established by said switching members.

2. A gas blast circuit breaker as defined in claim 1 wherein said gas supply tube is made of metal.

3. A gas blast circuit breaker as defined in claim 1 wherein said gas supply tube is made of electrically insulating material.

4. A gas blast circuit breaker as defined in claim 1 wherein said gas supply tube includes bores through the wall thereof at a location where the tube wall is spaced from the inner wall of said hollow insulator.

5. A gas blast circuit breaker as defined in claim 1 and which further includes means arranged in said annular passageway established between said stationary switching member and said gas supply tube for rendering uniform the flow of pressurized gas through said passageway.

References Cited UNITED STATES PATENTS 9/1949 Grunenald et al. 12/1950 Ainsworth et al. 200-148 X FOREIGN PATENTS 1,064,592 9/1959 Germany.

25 ROBERT S. MACON, Primary Examiner. 

